Process of making a smokeless explosive powder



Patented May. 10, 1927.

T curiae STATES PATENT OFF-ICE- smells I. no ron'r AND n'nimsr nu POINT, or wnu'me'ron, DELAWARE, assmuons T IL. 8, I. POWDER COMPANY, OF WILHINGTON, DELAWARE, CORPORATION OF DELAWARE.

I No Drawing.

and of flashless, or substantially flashless,

properties, wherein soluble nitrocellulose 1s intimately admixed with a flame propagating agent, which may be black powder or may be a nitrate, in the presence of a liquid, the liquid being one adapted to colloid or aid in colloidingthe nitrocellulose; all as more fully hereinafter ,set f o'rth and as .claimedi" Colloidedtorms of soluble nitrocellulose forma wellknown type of smokeless pow-. der. Colloiding isthe technical-term'fon treating nitrocellulose with various solvents in greater or less proportion, so that its original structure is obliterated. The amount of solventmay be enough to effect a solution or as is usually the case'merely enough to plasticize. After colloiding, the solvent, or most of it, is removed; generally in such a way as to'enable its recovery. Some of the solvent used remains with theipowder and the properties of the final product are, to some vent. In this country, as a rulea mixture of extent, dependent upon this remaining solether and alcohol is used for colloiding; but other solvents, suchas acetone, 'amyl acetate,

7 ethyl acetatean'd various esters of the fatty acids-etc. etc. are sometimes used for special purposes. After, colloiding, the powder is ordmarilyformed into perforated grains; the term grain in this art meaning any unit of any size or shape adapted to be used in assembling a propellant charge for cannon. -It is common practice tomake each grain cylindrical, with longitudinal perforations, usually s'even in number. In the.

ordinary way of manufacturing, the colloided' material is forced through suitable dies which form it into perforated strings and these strings arethen cut'ginto short lengths, forming grains. The'a'ibject of the perforations in the grains is Ito give a progresslvely Increasing surface area for combustion and, thereby, an accelerating pro- IBOCESS O]? MAKING A SHOKELESS EXPLOSIVE I A A Application filed November 10, 1925. Serial No. 88,224.

duction of gases. In the combustion of smokeless powder, burning is pro rtional to the surface area. including interlor burning areas such as are afforded by the rforations, and the rate of development 0 combustion gases per'tlme unit progressively ,in-

creases until just before the powder perishes and disappears. v

With this type of owder used in ordnance, as the projectile-emerges from the gun, there is a brilliant flash or flame .extending a considerable distance from the muzzle. I burning of-nnburnt materials by admixture This flame is, apparently due to.

with the oxygen of the ain". In other words,

is a secondary combustiofi'or explosion beyond the muzzle. Nitrocellulose does not contain suflicient oxygen for complete combustion.

This flash is highly objectionable from a military point of view and it'is' desirable to obviate it. In certain prior and copending applications, we have described and claimed methods of producing flashless'powders and products of such methods. In a general way, the method whereby we have been enabled to obviate flash consists in giving the colloided powder a -short of honeycomb structure withwhat we have called a flame propagating agent sealed in within the cells. The powder grain may be, and usually is, perforated in the ordinary way. With the vcellular structure just described and with flame propagating agents in the cells, a new type bf. progressively increasing combustion is aflorded and this may be, and usually ,is, superadded to the type given by the perforations. The fla'me propagating agent may, or may not, deliver a certain amount oi oxygen to compensate for the deficiency in oxygen of the nitrocellulose. With an oxidant ,used to compensate for such deficiency,

unburning gases are delivered at the muzzle.

With other types of flame' propagating gas expansion are heat absorbing, while comagainst each other.

bustion is heat developing; these balancing powders, the maximum heat evolution is postponed in such a manner as to cause the gases leaving the muzzle to be very hot. By superadding the new type of acceleration, the condition of the gases leaving the muzzle is changed and they do not ignite; the

coal, with or without sulfur.

flash is not produced.

As flame propagating agents, we have successfully used a wide variety of different materials; some oxidants and some Among the non-oxidants is ordinary black iowder; and various mixtures of the same type, containing potassium nitrate'and char- Black powder, being quicker burning than colloided nitro-cellulose, as the flame reaches and opens a cell containing it, the black powder disappears, leaving a-pit or cavity giving new surfaces along which combustion now takes place. The same result, flashlessness, is accomplished in another way if the included solid in the cells be one giving ofi oxygen when heated, such as potassium nitrate, potassium bichromate, etc. The evolved oxygen quickens the combustion locally along the interface between the nitrocellulose and the included particles. The result is the same: that of opening a new cavity or pit. In addition, the evolved oxygen tends to compensate for the oxygen deficiency of the nitrocellulose.

In an application filed June 12, 1918, under the Serial No. 239,531, we described and claimed a flashless powder. In this invention, soluble nitrocellulose and nitrate of ammonia (with or without some nitroglycerin) were'intimately mixed and were colloided with ether and alcohol; some acetone being usually added. The result was an integral mass of colloided nitrocellulose contaming included crystal fragments of nitrate of ammonia. The grains produced by this method have, so to speak, a honeycomb structure with nitrate of ammonia crystal fra ments included within the cells.

11 another application, filed January 24, 1919, as 'Serial No. 272,857, we described and claimed a flashless powder having the same honeycomb structure and containing a mixture of potassium and barium nitrates with-',

in the cells; and we also described a method of producing this powder wherein the nitrocellulose and the flame propagating agent were thoroughly mixed and incorporated, as by treating in a standard-black powder mill in the presence of a suitable blending liquid; the blending liquid serving to prevent dusting and danger. Afterwards, the blending liquid was removed and the nitrocellulose, which now existed in mechanical mixture with the flame propagating agent, was colloided to make it integral and give the,

In ordinary perforated nothoneycomb structure. The operation was, so to speak, a 2-stage operation with two diiferent liquids employed; one in the mix ing stage and the other in the colloiding sta e.

I ii another application, filed April 24, 1920, as Serial No. 376,267, we described the same method of operation in making a flashless powder. The specific flame pr0pagating agent described and claimed in this application was black powder. I

In another application, filed February 23. 1921, as Serial No. 417,229, we described and claimed the making of a flashless powder wherein the flame propagating agent was potassium bichromate and charcoal. The same 2-stage method of operation was employed in manufacture.

As the blending liquid to he used in these processes, there could be used anything not having solvent power on the nitrocellulose. lVe described particularly water and gaso line. We have now discovered that a simpler, cheaper and more efficient operation may be accomplished by using as the blending liquid one which is subsequently useful in colloiding. The liquid to be used in colloiding, itself may be used in blending. In this stage of the operation, simple .mechanical mixing only is wanted. The amount of moistening liquid required during blending is very little; merely enough to prevent dusting and incident dangers; and this amount may be, and usually is, too little to effect any substantial colloiding of the nitrocellulose during the time required for blending, even where the blending liquid is an active solvent, such as a mixture of-alcohol and ether. Its presence'in no way prevents even and thorough admixture of the nitrocellulose, which is usually in the form of relatively short fibers, and the solid flame propagating agent, which is usually in the form of a rather fine'powder. W'e may effect admixture and incorporation in' a standard black powder mill. Or we may employ ordinary commercial kneading and mixing machines. -The particular apparatus used is immaterial, as long as a very intimate mechanical admixture can be made.

In one embodiment of the present process we use alcohol as the blending liquid. This is not a solvent for nitrocellulose and thercfore effects no colloiding. In its presence simple mechanical mixing, which is what is here wanted, is facilitated. After the incorporation, the excess of alcohol, if any, is di tilledofl, and then the required amount of ether added.

In other embodimentsof our invention, the liquid used in blending is the ordinary ether-alcohol mixture employed for colloiding. If merely the amount necessary to preill) vent substantial dusting and afford a certain amount of lubrication be em 10 ed, no material colloiding takes place urmg the mixi operation under ordinary mixing GOIIdltlODS, More of the ether-alcohol mixture'can be'added later to efiect colloidin 'However it is possible to secure good .a

mixture of the nitrocellulose with the flame propagating agent in the presence of the.

liquid later to be used as a colloiding solvent and have the solvent act merely as a blending agent during admixture, even where it is present in the full amount required for colloiding, there bein no such colloiding or solution of nitroce lulose as will cement the fibers together and prevent uniform admixture. Colloidin takes place later when the mass is subjec to pressure.

The uestions of whether theterm colloiding is etymologically correct, and of g the extent .to which the solvent actually acts upon "the fibers are subordinate to the prac tical consideration that during the mixing operation, the mass of nitrocellulose, flash eliminating compound and solvent is not in such a physical condition as to prevent the thorough mixing in and' uniform distribution through the mass of the dash eliminating compound. After pressure is applied it would be practicall impossible to .mix any other solid material lose, as it is then in the condition of a stifi rubber-like mass which will flow only when subjected to great pressure, while before pressure is ap lied it is scarcely difi'erent from a mass 0 slightly damp meal, which can be readily stirred. Naturally, much depends upon the physical characteristics of the two substances mixed,

If the mass during the kneading or mixing operation contains alcohol only, any ex cess' may be removed by. distillation and then the appropriate amount of ether added 7 and mixed. If a small amount of a mixture of ether and alcohol has been used as the blending liquid, any deficiency can be compensated for by an addition of solvent prior to removing the mass from the kneading or mixing machine.

After admixture is perfected, the mixed materialsare ordinarily in the form of a moist, but not wet, mass. The moist mass may be at once given what may be called a rough pressing operation; may be converted into blocks in any suitable machine by the use of comparatively low pressures, The object of this operation is to facilitate. handling. The blocks are then transferred to a machine in which the material can be subjected to a heavy pressure, usually about 6060 pounds r square inch. By this res- ,sure and during it, colloiding is comp eted and the material is converted into an apparently homogeneous plastic mass: Actually, it is. an integralccllular mass of nitrocelluwith the nitrocellu-,-

tion materially greater than that of col- I loided nitrocellulose, such as the various y'ariches of black powder; 6 or any oxygen evolving solid, such as the various nitrates. The solid within the cell, being eflectually sealed in against access of air, various hyoscopic nitrates and other oxygen yieldmg. salts may be employed which are not -ordinarily suitable in this class of powders.

For example, sodium nitrate may be so used. However, ordinarily, we prefer pofassium nitrate, barium nitrate, or a mixture of both.- Strontium nitrate may be employed." Various bichromates and chromates give good results in making fiashlss powder. Po-v tassium bichromate is particularly suitable. With any of'these oxidants, the salt may be admixed with a little charcoal to take up its excess of oxygen. It then acts in the same manner as black powder. On the whole, nitrates and chromates give the most satisfactory results and are better than other oxygen yielding compounds, such asz may be used for special purposes. -Manganese dioxid, alone or -in admixture with other materials, is sometimes useful; as are peroxid of lead and oxid of mercury.

In using black powder, we ordinarily employ what is known as meal powder. Usu-, ally, we desire the included flame propagating agent in rather fine form: that is,' we dechlorates and perchloratesw These, however,

ill!

sire rather'small cells in the honeycomb structure.

In a specific embodiment of the present process making a flashless powder adapted for use in 5 inch guns under service conditions, we proceed as follows: i

We take 5 parts of meal which is generally fine enough to pass a mesh screen, and place it in a standard black wder wheel mill with 100 parts of pulpe nitrocellulose which contains 23 per black powder cent of its dry weight of alcohol. These ingrcdient-s are incorpgrated for a sulficient time.

to.,g ive uniform admixture-generally about 50 minutes. The mixture is then placed in a mixing machine and ether, containing diphenylamine in solutionv is added. The

,amount of ether used is about43 per cent of the dry .weight of the nitrocellulose, and contains suflicient 'diplienylamine, sothat the finished powder will contain 0.5-per cent of this material. The use of diphenylamine is not peculiar to fiashless powder, as this material, in the amount mentioned, is common- 1y used as a. stabilizing agent in all nitrocellulose powders. After the ether is added incorporation is continued until a uniform product is obtained-generally for about 50 minutes. It is understood that the periods given for incorporation are merely exemplificator and are subject to wide variation, depending upon the temperature, speed, size and type of the mixers. If another colloids ing solvent than ether-alcohol is used, as may be the case, a further. adjustment of conditions becomes necessary. The vital matter is thata uniform admixture of the ingredients be obtained. The mixture is then put into a block making press and given a pressure to solidify it somewhat. It is then transferred to a hydrauliepress operating under about 6000 pounds pressure from which it is forced through suitable dies to give longitudinal strings or cords having the usual seven longitudinal perforations. In making this particular powder the strings are cylindrical and about inch diameter.

The strings are cut into inch lengths and are dried in the usual way so as to recover the solvent.

I'Vhat we claim is 1. In the manufacture of a flashless, smokeless propellant powder, the process which comprises mechanically mixing and blending nitrocellulose and a flame propagating agent, blending being performed in the presence of a liquid having utility in colloiding nitrocellulose but effecting no colloiding during mixing, and afterwards completely colloiding the nitrocellulose.

2. In the manufacture of a flashless, smokeless propellant powder, the process which comprises mechanicall mixing and blending nitrocellulose and lack powder, blending being performed in the presence of a liquid ha-vin utility in colloiding nitrocellulosebut e ecting no substantial colloiding during mixin and afterwards completely colloiding t e nitrocellulose.

3. In the manufacture of a flashless, smokeless propellant powder, the process which comprises moistening nitrocellulose and a flame propagating agent with alcohol and mixing and -blend1ng the moist substances, thereupon adding ether and comcolloiding the nitrocellulose.

\ the [manufacture *of a flashless, smokeless propellant powder, the process WhlCh comprises moistening nitrocellulose I and black powder withalcohol and mixing and blending the moist substances, thereupon addin ether and completely colloiding the nitroce ulose.

A 5. In the manufacture of a flashless,

smokeless propellant powder, the process blendingnitrocellulose and which comprises: mechanica'll .mixing and v flilack powder in the presence of alcohol as aimoistening and lubricating liquid, thereupon adding ether to convertfthe alcohol into a colloiding solvent, completely colloiding the nitrocellulose and forcing the material so obtained through a die press under heavy pressure, the dies being adapted to type of perforated grain.

6. In the manufacture of a flashless, smokeless propellant powder, the process which comprises mechanically mixin and blending nitrocellulose and black pow er in make the usual the presence of alcohol as a'moistening and lubricating liquid, thereupon adding ether to convert theialcohol into a colloiding solvent, completely colloiding the nitrocellulose pressing the mixture to-obtain blocks, and forcing the material soobtained through a die press, under heavy pressure, the'dies being adapted to make the usual type of;perforated grain. 1

'7. In the manufacturev ,of a .fl'ashless,

smokeless propellant powder, the process which comprises mechanically mixing and blending nitrocellulose and a flame'propagating agent, in the presence of a liquid having utility incolloiding nitrocellulose but exercising no substantial colloiding during mixing.

8. In the. manufacture of a fiashles's, smokeless propellant powder, the process which comprises mechanically mixing and blending nitrocellulose and black powder, in

the presence of liquid having utility in colloiding nitrocellulose but exercisingno sub stantial colloiding during mixing.

9. In the) manufacture of a flashless,

smokeless propellant powder, the process which comprises moistening uncolloided nitrocellulose and a flame. propagating agent with ether and-alcohol and mixing and blending the moist substances without substantially colloiding the.- nitrocellulose.

10. In the manufacture of a flashless,

smokeless .propellant ,powder, the] process which comprises moisteninguncolloided nitrocellulose and black powder-with ether and alcohol and mixing. and blending the moist substances without-substantially colloiding the nitrocellulose. w 1

11. In the ,manufactur ofa fiashless, smokeless propellantfpowder; the process which comprises ,lilechanically v mixing and blending nitrocellulose and black powder in the presence of alcohol and ether as a moistening and lubricating liquid under conditions thereafter com letely colloiding, the nitrocellulose and tained through a die press under heavy prespreclud-ing substa-ntial colloiding,

orcing. the material so obsure, the dies being adapted to -make,:t.he I

usual type of perforated gramme- 12. In the manufacture of: flashle s s smokeless propellant powder the process which comprises mechanically mixin and blending nitrocellulose and black powi ier in the presence of alcohol and ether as a moistening and lubricating liquid under conditions precluding substantial colloiding, pressing the mixture to obtain blocks, and forcing the material so obtaiuedthrough a die press under heavy pressure, the dies being adapted to make the usual type of perforated 1 grain and colloiding being efiected during the pressing operations.

In testimony of which invent-ion, we have hereunto set our hands, at Wilmington, Delaware, on this fifth day of November, 1925.

, "FRANCIS I. DU FONT.-

ERNEST DU PONT. 

